Safety switch



April 1941 E. M. MILLER 2,237,262

SAFETY SWITCH Original Filed May 4, 1936 INVENTOR Ernesi M- Miller BYfli ht ATTORNEY Patented Apr. 1, 1941 @rlglnal application May 4, 3936,Serial No,

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W558. Divided and this application @ctohe 25, 193i, aerial No.l'ZllfiiEt 18 Claims. ((U1- Wil -122) Another object of the invention isto provide a time switch comprising a bimetallic element which isactuated by a heater to trip a latch to cause the switch to open.

Another object is to provide a switch of the above type wherein thebimetallic element is compensated for variations in .ambienttemperature.

Another object is to provide a switch which will open automatically atthe end of a given time interval, and means for adjusting the length ofthis time interval.

Still another object is to provide an automatic switch which will openafter a predetermined time interval and wherein a means is provided formanually resetting the device.

A further object of the invention is to provide a switch which willautomatically trip to open position upon the occurrence of apredetermined condition by means of a thermostatic latch, and whichcannot be closed by the manual reset mechanism until the thermostaticlatch is in a position to hold the switch closed.

A further object of the invention is to provide a switch of the abovetype wherein the switch will not close until the latch has been resetand the manual means released.

A still further object is to provide a safety switch requiring a manualresetwhereinthe main stress exerted on the spring contact arms isexerted thereon by the manual reset lever which has a very limitedmotion whereby said spring contact arms are saved from undue stress andstrain.

Other objects will become apparent to those skilled in the art as thespecification is considered having reference to the accompanying drawingin which:

Figure 1 is a side elevational view of the switch, parts of thesupporting structure being shown in section;

Figure l and looking in the direction of the arrows;

Figure 3 is a perspective view of certain portions of the structureshown in Figure 2 in a different operating position; and

Figure 4 is a detail view showing the thermostatic latch. and electricheater therefor and taken on the line 3-6 of Figure 2.

This application is a division of my co-pending application serialnumber 77,758, filed May 4, 936, now Patent 2,175,720.

The switch mechanism is all mounted upon an insulating panel it andsupported bya mounting bracket M which has at one extremity a downwardlydepending portion 62 and at the other extremity a second downwardlydepending portion 113. As better shown in Figure 3, portion l3 has anaperture 84 therethrough. A pair of spring leaf contact members l5 andit is carried by bracket ill and secured thereto by screws ll, whichpass through an insulating panel it and relatively large apertures inflange 12 into panel i0, and thus serve not only to support contactmembers l5 and it but also to maintain bracket M in related assemblywith panel ill through the frictional engagement of panel it and panelit with opposite sides oi flange ii. The, enlarged apertures which mayif desired be filled with suitable insulating washers are to precludeany electrical contact between flange l2 and screws ill which, it willbe seen, are in electrical engagement with members it and to. Members 65and it bear on their adjacent surfaces opposed contacts l9 and 20, theseparation of which serves to break a circuit for a purpose to behereinafter described. Adjacent the extremities of contact members 55and i6 and supported by bracket ii is a pivot pin 29, which has mountedthereon a manually operable lever 22, comprised of insulating materialto preclude interference with a circuit through arms l5 and i6. Lever 22has an arcuate portion 23 at an extremity thereof, adapted, undercertain circumstances, to abut an upwardly extending portion 24 ofcontact member l6. Also carried by pin it is a bracket member 25, whichhas a lateral extension 26 and a vertically extending portion 2! (seeFigure 3). Extension 21 is adapted to be engaged, under certaincircumstances, by a projection 28 of member 22. Bracket member 25 alsohas rigidly associated therewith a circular portion 29 also comprised ofinsulating material. A mounting member 30 is connected to bracket H, asby a screw 30 and a screw I Figure 2 is a. view taken along the line 2-2of 32 in a slot 33 which latter permits adjustment of the assembly withrespect to extension 26. Two bimetallic strips 35 and 35, securedtogether as by a stud 36, are suitably secured to mounting member 30.Mounted adjacent member 35 is a resistance element comprised of a coil37 having wires 38 leading thereto from suitable terminals 3d carried bya depending insulating panel 60, secured in any desired manner tobracket ii. Rigidly secured to the free end of bimetal strip 35 and onthe opposite side of coil 3? is a third bimetal element Lil, which has,as better shown in Figures 3 and 4, an upwardly extending portion :32adapted, under certain circumstances to be set forth hereinafter, toengage extension 25. v 1

The disposition of the component metals of strips 34 and 351s oppositein order that a change in temperature value applied equally to both willcause a balancing movement of the two strips.

in opposite directions. In other words, the positioning of strips so and85 is designed to overcome the efiect of ambient temperature changes onthe assembly. Resistance M is positioned, as above stated, adjacentstrip 35 and heat therefrom accordingly aflects strip 35 more stronglythan strip as to overcome the compensating effect. Element (ii is soarranged that temperature change will occasion movement thereofcorresponding to the movement of strip 35 and since heat from resistance31! is supplied to both strips 35 and All, such temperature rise will bythe multiplication of energy occasioned by the two elements readilyovercome any resistance offered by element 36.

In operation, when a circuit passes through coil 31 the bimetal assemblycomprised of elements 36, 35, and 6! tends to expand and thearrangement, as above stated, is such that such expansion causes theassembly to move in a direction away from contact carrying members 85and It. Upon such motion, portion 62 will move beyond the end ofextension 26, which, due to the spring pressure exerted on portion 29 byspring contact carrying member is, will immediately drop into theposition shown in Figure 3, which permits contacts i9 and 20 to separateand due to the pressures of arcuate portion 23 against extending portion26 oil spring contact arm' I 6, contact 20 will be precluded. frommoving with contact it as the latter moves away. Extension 26 alsoserves to hold the bimetal assembly in the position shown in Figure 3until such time as lever 22 is moved manually to the left, as seen inFigure 2. Upon such motion, projection 28 engages extension 21 and liftsextension as out of engagement with projecting portion 32. Since thebreaking of contacts 59 and 2e serves to break the circuit through coil37! the bimetal assembly will cool substantially immediately after thecessation of heat in coil 37 and upon the raising of extension 26 bymovement of manual clearance upon movement of lever 22 to the left,curved portion 23 will first engage extension i l to move it to theright. After the clearance above mentioned has been closed, projection28 will engage extension 21, which will in turn move circular member 29a short distance to the right until such time as extension as clearsprojection 42. Then upon release of lever 22, the spring pressure, asabove described, will permit the parts to return to normal position andthe contacts i9 and 20 to close.

From the foregoing it will be seen that all stress on the movable partsof the device, such as projection 26 and contact bearing arms l5 and I6is transmitted directly thereto from lever 22 and that no strain otherthan normal spring pressure is placed upon contact bearing arms I5 and I6. In other words, movement of lever 22 causes projection 28 to moveextensions 2? and 2e and circular member 29 to move contact arm l5, andpressure of arcuate portion 23 against extension 26 causes movement ofcontact arm it.

By this means, the resilience of arms l5 and it is less apt to beimpaired, the life of the switch is lengthened, and more emcientoperation assured.

Many modifications of this invention may occur to those skilled in theart, and it is therefore to' be distinctly understood that I am not tobe limited to the particular embodiment disclosed but rather by thescope of the appended claims.

I claim. as my invention:

1. A 'switch comprising a pair of resiliently mounted contacts, a pairof pivoted levers one end of each engaging one of the contacts to moveit against the resilience of its mounting, a oneway driving connectionbetween one of said levers and the other, means for rotating said onelever and hence said other lever through the one-way driving connection,a thermostaticlatch for preventing return of said other lever uponrelease oi said first lever, and means for heating said thermostat tocause it to trip the latch.

reset lever 22 returns to its normal or closed.

position. Contacts l9 and at close and the device will be ready torepeat the previously described cycle of operation.

It may here be pointed out that due to the configuration of lever 22,contacts 89 and so will not close until lever 22' has been manuallymoved to the left and released whereupon pressure of spring arm i8 andextension 241 against circular member 29 and curved member 23, re-

.spectively, will return the switch to its normal 2. A switch comprisinga pair of resiliently mounted contacts, a pair of pivoted levers one endof each engaging one of the contacts to move it against the resilienceof its mounting,

a one-way driving connection between one of said levers and the other,means for rotating said one lever and hence said other lever through theone-way driving connection, a thermostatic latch for preventing returnof said other lever upon release of said one lever thus causing switch010-- and hence said other lever through the one-way driving connection,a bimetallic blade having an and engaging said other lever under normaltemmounted contacts, a pair of pivoted levers one end of each engagingone of the contacts to move a generally U-shaped member, the other endof acstgecc the first thermostatic element being connected to a supportand the other end of the second thermostatic element engaging saidsecond lever, and heating meansdisposed between the two thermostats toheat them both and cause them to bend in the same direction to cause thesecond element to release the second lever to cause switch opening.

5. A switch comprising a pair of resiliently mounted contacts, a pair ofpivoted levers one end of each engaging one of the contacts to move itagainst the resilience of its mounting, a one-way driving connectionbetween one of said levers and the other, means for rotating said onelever and hence said other lever through the oneway driving connection,a thermostaticlatch for preventing return of said other lever uponrelease of said first lever thus causing switch closure, said latchcomprising two bimetallic thermostats connected together at one end toform a generally U-shaped member and being arranged to flex in the samedirection on temperature change, one end of the first thermostat beingconnected to one end of a third bimetallic thermostat mounted on asupport at its other end and arranged to flex in the opposite directionfrom the other two and of a size to just compensate them for changes inambient temperature, the other end of said second thermostat engagingsaid second lever, and heating means disposed between the first andsecond thermostats to heat them and cause them to bend in a direction tocause the second thermostat to release the second lever and cause switchopening.

6. A switch comprising a pair of resiliently mounted contacts, a pair ofpivoted levers one endoi each engaging one of the contacts to move itagainst the resilience or its mounting, a-oneway driving connectionbetween one of said levers and the other, means for rotating said onelever and hence said other lever through the one-way driving connection,a thermostatic latch for preventing return of said other lever uponrelease of said first lever thus causing switch closure, said latchcomprising two bimetallic thermostats connected together at one end toform a generally U-shaped member and being arranged to fiex in the samedirection on temperature change, one end of the first thermostat beingconnected to one end of a third bimetallic thermostat mounted on asupport at its other end and arranged to flex in the opposite directionfrom the other two and of a size to just compensate them for changes inambient temperature, the other end of said second thermostat engaginguaid second lever, and heating means disposed between the first andsecond thermostats to heat them and cause them to bend in a direction tocause the second thermostat to release the second lever and cause switchopening, the support or said 70 third thermostat comprising a platemounted for. rotation about a pivot so that the thermostatic latchassembly may be adjusted relatively to the two levers.

7. A switch comprising a pair of resiliently 75 mounted contacts, a pairof pivoted levers one end 01 each engaging one of the contacts to moveit against the resilience of its mounting, a oneway driving connectionbetween one of said levers and the other, means for rotating said onelever and hence said other lever through the one-way driving connection,a first thermostat mounted at one end on a support and connected at itsother end to one end of a second thermostat the other end of whichengages said other lever for preventing its return upon the release ofsaid first lever, said first thermostat being arranged to respondoppositely to said second thermostat in order to compensate it forchanges in ambient temperature, and means for heating said secondthermostat to cause it to disengage said other lever.

8. A switch comprising a pair of resiliently mounted contacts, a pair ofpivoted levers one end of each engaging one oi! the contacts to move itagainst the resilience of its mounting, a oneway driving connectionbetween one of said levers and the other, means for rotating said onelever and hence said other lever through the one-way driving connection,aflrst bimetallic thermostat having one end cooperating with said otherlever under normal temperatures thus preventing its return upon releaseof said first lever thus causing switch closure, a second bimetallicthermostat connected at one end to the other end of said firstthermostat and adapted to flex in the opposite direction therefrom ontemperature change, said second thermostat being mounted on anadjustable plate, and means for heating said first thermostat to causeit to flex from engagement with said other lever to permit it to rotateand open the switch.

9. A switch comprising a pair of leaf springs each carrying anelectrical contact, said contacts being in spaced relation when the leafsprings are in their normal position, a first lever having one endadjacent one of the leaf springs, a second lever having a one-way driveconnection with the first lever and having one end adjacent the otherleaf spring, manual means for rotating the second lever and hence thefirst lever through the one-way drive connection causing both leafsprings to move in unison and maintain the contacts spaced apart, latchmeans for preventing reverse movement of said first lever after apredetermined rotation thereof, said other leaf spring causing saidsecond lever to reverse upon release thereof which causes the electricalcontacts to engage, and means for tripping the latch to cause saidcontacts to open.

10. A switch comprising a pair of leaf springs each carrying anelectrical contact, said contacts being in spaced relation for normalpositions 01 said leaf springs, a first lever having an extension on oneof its arms, its other arm lying in contact with one of the leafsprings, a second lever having a projection lying adjacent saidextension and having one end lying in contact with the other of the leafsprings, a handle on said second lever forming a manual means forrotating it and the first lever through the projection and extension,said levers causing said leaf springs to bend in unison in the samedirection maintaining the contacts in spaced relation, latch meanstensioned to move into the path of said first lever after apredetermined rotation thereof, the other or said leaf springs causingreversal of said second lever upon release thereof, reversal of saidfirst lever being prevented by said latch thereby causing said switchcontacts to close, means to trip said latch, and stop means for limitingthe manual rotation of said second lever in one direction and therotation oi said second lever by said other leaf spring in the otherdirection.

11. A switch operating mechanism comprising,

thermostat, a pivoted lever one end of which engages said thermostat andthe other end of which engages the first of said contacts to hold it inswitch closing position against the resilience of its mounting, meansfor heating said thermostat to cause it to flex in a direction torelease said lever thus permitting the switch contact to move to opencontact position and to' rotate said lever about'its pivot, a secondlever having a portion adapted to engage the second switch contact andanother. portion adapted to contact the first lever, and means forrotating said second lever to cause rotation of the first lever andhence cause movement of both switch contacts simultaneously in the samedirection, release of said second lever permitting said second switchcontact to reverse its rotation and to cause two resiliently mountedelectrical contacts, a

switch closure providing the thermostat has cooled enough to engage thefirst lever and prevent its reversal.

12. A switch comprising a pair of resiliently mounted contacts, a pairof pivoted levers one end of each engaging one of the contacts to moveit against the resilience of its mounting, a oneway driving connectionbetween one of said levers and the other, means for rotating said onelever and hence said otherlever through the one-way driving connection,a thermostatic latch for preventing return of said other lever uponrelease of said one lever thus causing switch closure,

means for heating said thermostat causing it to expand and release theother lever and permit switch opening, and means for adjusting theamount of heat necessary to cause the thermostat to trip the latch.

. to form a generally U-shaped member, the other,

end of the first thermostatic element being connected to a support andthe other end of the second thermostatic element engagingsaid secondlever, heating means disposed between the two thermostatic elements toheat them both and cause them to bend in the same direction to cause thesecond element to releasethe second lever to cause switch opening, meansfor mounting said thermostatic elements on the same support and meansfor adjusting said support.

14. A switch comprising a pair of resiliently mounted contacts, a pairof pivoted levers one end of each engaging one of the contacts to moveit against the resilience of its mounting, a

one-way driving'connection between one of said levers and the other,means for rotating said one lever and hence said other lever through theone-way driving connection, "a thermostatic latch for preventing returnof said other lever upon release of said first lever .thus causingswitch.

aaaaeae 1 closure, said latch comprising two bimetallic thermostatsconnected together at one end to form a generally U-shaped member andbeing arranged to flex in the same direction on temperature change, oneend. of the first thermostat being connected to one end of a thirdbimetallic thermostat mounted on a support at-its other end and arrangedto flex in the opposite direction than the other two and of a size tojust compensate them for changes in ambient temperature, the other endof said second thermostat engaging said second lever, heating meansdisposed between the first and second thermostats to heat them and causethem to bendin a direction to cause the second thermostat to release thesecond lever and cause switch opening, and means for adjusting theamount of heat necessary to cause the second thermostat to-reiease thesecond lever.

15. A switch comprising a'pair of leaf springs each carrying anelectrical contact, said contacts being in spaced relation when the'leafsprings are in their normal position, a first lever having one endadjacent one of the leaf springs, a second lever having a one-way driveconnection withthe first lever and having one end adjacent the otherleaf spring, manual means for rotating the second lever and hence thefirst lever through the one-way drive connection causing both leafsprings to move in unison and maintain the contacts spaced apart, latchmeans preventing reverse movement of said first lever after apredetermined rotation thereof by said second lever, said other leafspring causing said second lever to reverse upon release thereof whichcauses the electrical contacts to engage, means for automaticallytripping the latch after a predetermined time to cause said contacts toopen, and

means for adjusting the time necessary for tripping the latch.

16. A thermal cut-out comprising a. pair of leaf springs, a contactcarried by each, a retainer for biasing one of said leaf springs toposition with its contact engaging the other contact, a bimetal latchfor said retainer, said latch upon releasing said 1retainer permittingone of said leaf springs to move to position with the contact carriedthereby out of engagement with the other contact, a heating element forso unlatching said latch upon predetermined current flow through saidheating element and manual means for relatching said retainer, saidmeans being engageable with said retainer to move it to latched positionand simultaneously engageable with said other leaf spring to move it ina direction separating the contact carried thereby from the contactcarried by one of said leaf springs.

17. A thermally operated current responsive switch of the classdescribed, comprising, in combination, a support, a first spring contactblade having one of,its ends fixedly secured thereto, a second springcontact blade also having one of its ends fixedly securedto said supportnear the fixed end of said first spring contact blade and extendingsubstantially parallel to said first blade, said spring contact bladesbeing normally blades to locking position after they have been released,said manual means maintaining said contact blades in open circuitrelation during the locking operation.

18. A thermally operated current responsive switch of the classdescribed comprising a pair of electrical contact carrying blades eachanchored at one end and biased away from each other to normally open thecontacts, a bimetal strip thermal element and means for operativelyassociating the thermal bimetal strip element with the contacts tonormally afford endwise resistance by the bimetal strip to openingmovement of the contacts, warpin movement of the bimetal strip underinfluence of heat shifting the end of said bimetal strip to permit thecontacts to open under their normal bias, the parts being so arrangedthat upon removal or breakage of the himetal strip the contacts willseparate, and means for resetting said contacts to closed positioncomprising a movable member separately moving each of said contactblades to retain them separated until the thermal bimetal strip has beenendwise engaged to retain one of said contact blades in its resetposition before the other contact blade is permitted to engagetherewith.

ERNEST M. MILLER.

